Generally, straps or bracelets, made of leather or metal are fixed to the horns of a watchcase, via a bar formed of a tube, in which are mounted two pistons that can move in translation, and an elastic member arranged between said pistons which tends to drive them towards the exterior of the tube. Said bar is mounted in a housing provided for this purpose at one end of the strap or bracelet, and the pistons are engaged in blind bores made facing each other in the horns of the case.
To remove a strap or bracelet secured to a case in this manner, a tool is required, designed to push the pistons back into the tube, against the force exerted by the elastic member, and thereby remove the pistons from the bores. The person wearing the watch does not permanently have such a tool available and, further, the use thereof can be inconvenient. This is why straps and bracelets provided with this type of securing device are generally permanently attached to the watch.
There also exist securing devices that allow the strap or bracelet to be removed from the case without using a tool. Such devices usually include a bar, of the type described above, on which a member for actuating the pistons is mounted, passing through the tube. Said actuating member is, for example, a radial finger integral with one of the pistons, as described in CH Patent No 327838. The finger is slidably mounted through an axial slot made in the tube and the movement thereof along the slot pushes one of the pistons back inside the tube. In CH Patent No. 697152, the actuating member is a push-button movably mounted radially through the tube. The pistons are provided with support surfaces located opposite each other when the two pistons are head to tail inside the tube. The push-button includes two arms that cooperate with said support surfaces so as to draw the pistons towards the inside of the tube when said push-button is pushed in.
The securing devices thus described are generally used for interchangeable straps or bracelets, which can be replaced as the user desires. They are not, however, free of drawbacks. It will be noted, in particular, that they require major structural alterations to the bar, such as, for example, making an opening in the tube, or transforming the pistons. These changes lead to significant increases in manufacturing costs. These securing devices further include a projecting element, namely the actuating member, which may become caught on or injure the person wearing the watch.